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  1. #1
    Join Date
    Nov 2018
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    Melbourne
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    Default Simple box with beveled corners. What am I doing wrong?

    Hi All

    I'm currently in the process of making some basic boxes before embarking on some larger projects. However I'm having a lot of trouble getting the cuts/joinery right using my table saw.

    Here's a photo of the simple box which I'm trying to make: note the edges don't join correctly. I've just used masking tape to hold the piece together, clamping is only serving to move the sides around rather than assist with proper alignment.

    20190818_165444.jpg

    Steps taken to get to this point:

    1. Built a crosscut sled to cut the bevels. This involved gluing 2 miter bars to the bottom of a piece of ply and attaching a front and rear fence. The front fence has been adjusted using the 5 cut method so that it is square with the blade. I've also ensured theres no play or wobble in the miter bars. The fence I have built is similar to the one here: YouTube
    2. Adjust the blade bevel to 45 degrees (checked by using a digital angle guage - placed on table saw top, reset gauge to zero, adjust bevel of blade to 45 degrees).
    3. Clamp a stop block on the front fence at the left of the blade, ensuring consistent length of all four sides of the box
    4. Make a first beveled cut at 45 degrees. I'm noting to clamp the work piece tightly down against the sled and against the front fence.
    5. Flip the wood over and rotate to make the remaining cuts.

    Any clues as to what I may be doing wrong? Fairly discouraged at this point, but sure something in my process is not right.

    Thanks in advance.

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  3. #2
    Join Date
    Oct 2014
    Location
    Caroline Springs, VIC
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    1,508

    Default

    Four corner miter joints = the hardest joint in woodworking by a country mile!

    The problem is that your angle is greater than 45. You need to tilt the blade a little further. Treat the digital angle gauge as a good start and then refine from there from the actual cuts instead of the readout on the gauge.

  4. #3
    Join Date
    Apr 2019
    Location
    AU
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    Default

    When you "zero " your angle gauge, do you do it on the surface of your sled, not the table saw?
    I found that can make that fraction of a degree difference.
    I still prefer to refine my mitres on a shooting board though!

    Sent from my SM-G973F using Tapatalk

  5. #4
    Join Date
    Oct 2007
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    Alexandra Vic
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    Default

    Some potential issues that I can anticipate;

    Have you checked the flatness of the table saw top?
    Is it pressed metal or cast?
    A pressed metal top will rarely be flat or consistent across its surface, so the point on the top where you zero the digital angle gauge becomes way more critical for setting the blade angle accurately, similarly, a poorly machined cast top may be almost as bad.

    Are the mitre gauge slots identical depth?
    Are the runners on the sled slightly shallower than the slots in the table?
    If the table top is flat, the sled should be allowed to slide across the top of the table, and just use the runners as guides. If the runners are contacting the bottom of the slot, they may be skewing the top surface of the sled slightly out of parallel with the table top if there is any discrepancy in slot depth. My experience of mitre slots on lower price bracket table saws has been that manufacturers often struggle to get two slots parallel, and of equal width and depth, unfortunately an attitude of 'if it looks like a table saw at 1m distance it can be sold as one' seems to prevail.

    Is the plywood used for the sled base truly flat, void free and of consistent thickness. Any of these errors will complicate setting up for the cuts you are making, particularly as the parts you are making are quite short relative to the thickness of the material. I would definitely advise following Brian's suggestion of establishing your angle gauge zero from the top of the sled and basically as close as you can get to the blade without touching it.
    I used to be an engineer, I'm not an engineer any more, but on the really good days I can remember when I was.

  6. #5
    Join Date
    Mar 2008
    Location
    Hobart, Tas
    Posts
    363

    Default

    Don't be discouraged. You'll get there, it will just take a bit of trouble shooting. And the next time you come across this issue, you'll know what to do.

    Using thick stock is tricky as it amplifies any errors in your setup. The good news though is that once you nail thick stock, thinner stock will be a doddle.

    From your photo it looks as though the gap is consistent along the length of each joint. Can you confirm this? If that is the case, the issue is with the angle not being 45 deg, and others have given you good suggestions to try.

    If the gap differs from one end to the other, the issue it's most likely with the angle between the blade and sled fence. One thing to check is for sawdust against the fence, which will stop your stock being able to register perfectly against it. A trick when building sleds is to provide some relief at the base where sawdust can "hide".



    Also, if you use masking tape to "roll up" the box (common technique for small boxes), it is pretty clear if the box isn't rolling up square, again pointing to the fence/ blade not being a perfect 90 deg.

    Now having said that, no matter how hard I try, mine never line up without at least a tiny step on the top and bottom, but that's simple to plane flat after the glue up.

    Again, don't despair, you'll get there.

    Kind regards,
    Lance

  7. #6
    Join Date
    Dec 2003
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    lower eyre peninsular
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    Default

    take it from me, so far your not doing anything wrong, what you are doing is something just isnt right, that you shouldnt do again, we learn from others about out so called mistakes. learn from this dont be hard on yourself or discouraged mate, some of the guys here have made monumental stuffups, only difference is they have been too ashamed to admit it.
    You asked for advice, learn and teach yourself again.

    Biggest thing to remember ....timber is replaceable, digits aren't
    Life expectancy would grow by leaps and bounds if green vegetables smelled as good as bacon.

  8. #7
    Join Date
    Nov 2018
    Location
    Melbourne
    Posts
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    Default

    Hi Everybody

    Thank you all so much for the responses so far and the encouragement. It really helped to put me back in the right frame of mind for this project!

    I decided to take the simplest advise and re-check the bevel angle of the blade in reference to the sled base, not the table base. In hindsight this is a really obvious oversight. It turns out that the angle in relation to the sled was 45.20 degrees. This morning I made the adjustment, and have achieved some much better results. A photo below for proof.

    20190819_133329.jpg


    The cuts aren't absolutely perfect, however I'm pretty sure with some fine tuning using a shooting board (my next project, perhaps) the alignment would be almost spot on. the edges as they are now still look pretty good and with some light clamping and a little planing, I'd expect the joins to look quite good on a finished piece. What do you guys think?

  9. #8
    Join Date
    Mar 2008
    Location
    Hobart, Tas
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    Default

    Woo hoo!

    Great job.

  10. #9
    Join Date
    Dec 2003
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    lower eyre peninsular
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    70
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    2,080

    Default

    so whose a happy chappy? good to see
    Life expectancy would grow by leaps and bounds if green vegetables smelled as good as bacon.

  11. #10
    Join Date
    Nov 2018
    Location
    Melbourne
    Posts
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    Default

    Thanks guys! I am pretty happy to have gotten this one sorted

  12. #11
    Join Date
    Dec 2005
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    Huntington Beach, CA USA
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    The way that I have always done the cuts is with a dual side of the blade mentality.

    First - The height of the blade doesn't matter much, as long as it cuts all the way through the timber.
    Second - Set the blade to 45 or as close as possible.
    Third - Cut the front and back bevels with the fence to the right of the blade. Cut all 4 bevels w/o moving the fence during the second cut.
    Fourth - Cut the left and right sides with the fence to the left side of the blade. Cut all 4 bevels w/o moving the fence during the second cut.

    Effectively what you are doing is making the front / back pieces the same size and the bevels all with the same angle. With the fence moved to the other side of the blade, the left / right pieces are the same size AND the at the complementary angle to the front / back angles.
    Rich

    When SWMBO said "I won't cook in metric."
    The metric system died in the US.

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